The cabin air inhaled by passengers and flight crews on commercial airplanes has been linked to several alarming health concerns such as cancer, neurological problems and chronic fatigue, new research in the World Health Organization (WHO) journal states.

According to the Public Health Panorama report, the “bleed air” circulating within flight cabins is contaminated with neurotoxins and other chemicals from engine oil and hydraulic fluid (among other hazardous materials). Researchers say they’ve found a link to short- and long-term chronic and acute illnesses.

(“Bleed air” is a system that provides the cabin with ventilation and is used to pressurize the cabin, the report explains. All air crafts – with the exception of the Boeing 787 – use this system.)

And in 2015, more than 3.5 billion passengers and 500,000 pilots and crew members were exposed to low levels of such materials in the air, the report says.

Researchers looked at over 200 airline workers who had been exposed to such toxic air. The health effects recorded range from nose, eye and throat irritations, fatigue, nausea, cramps, skin reactions and reoccurring respiratory tract infections.

Chronic fatigue, chemical sensitivity, chemical exposure, soft tissue damage, as well as cardiovascular, neurobehavioural, neurological and respiratory symptoms have also been reported.

The report examined 15 circumstances when flight cabins filled up with contaminated air (occasions known as toxic air events) and found that there were seven occasions when the pilot or pilots were fully or partially incapacitated. Of those seven occasions, five had seen both pilots fully or partially incapacitated.

This isn’t the first time researchers have looked into exposure of chemical on air crafts.

While the presence of such chemicals were found to be present, researchers did not look into the potential health risks associated with exposure.

The issue of contaminated bleed air has been discussed among airline professionals for years – and it’s prompted many working within the industry to demand change.

The Canadian Union of Public Employees (CUPE) is the union representing over 10,000 employees who work for Air Canada, Air Transat, Calm Air, North Air, Cathay Pacific, First Air and Sunwing Airlines. And

And according to Troy Winters, senior officer of health and safety at CUPE, this is a battle the union and its members in the airline industry have been fighting.

“This report backs up what our members have been saying for years,” he said. “This is something we’ve been pushing back on for a long time. We’re actively in a few open court cases on whether or not this is a danger as per the Canada Labour Code.”

Much like WHO’s report, CUPE is concerned with synthetic lubricants, and other chemicals like de-icing fluid contaminating the bleed air, which is fed directly into the aircraft cabin.

The union says that at high temperatures, these product can degrade and become aerosolized. And as of today, there is no filtration system or equipment on board commercial flights to filtrate these toxic fumes.

“The first big step in fixing this is we look at the airplane designers themselves,” Winters said. “Going forward we need to design planes so that they don’t use the bleed air system. Of course that solution doesn’t fix all the planes that are in the air right now. So we need to find some way to filter the air as it enters the flight deck and cabin.”

Last year CUPE’s Airline Division presented its concerns to MPs on the standing committee on transport, infrastructure and communities and the committee agreed to conduct an investigation into aviation safety.

The report is expected to be wrap up in the fall.

Dr. Shawn Aaron, a respirologist from the Ottawa Hospital, says he’s seen two cases in the last six months where pilots presented with unexplained chronic pneumonia.

“They had both recounted that they had been exposed to vaporized fuels within the cockpit,” Aaron said. “It was the first I had ever heard of this issue so it had piqued my interest, so this is something I’ve been interested in, and then I see this report which seems to confirm that there may be a problem here with contaminated air in the airplanes.”

However, Aaron wants passengers to know that while there is a concern for everyone who travels by air, this seems to be more of an issue among pilots and flight crews who are regularly exposed to these types of chemicals.